Setup microSD card

For these instruction we are assuming, DISK=/dev/mmcblk0, lsblk is very useful for determining the device id.

export DISK=/dev/mmcblk0

Erase partition table/labels on microSD card:

sudo dd if=/dev/zero of=${DISK} bs=1M count=50

Create Partition Layout:With util-linux v2.26, sfdisk was rewritten and is now based on libfdisk.

sudo sfdisk --version
sfdisk from util-linux 2.27.1

sfdisk >= 2.26.x

sudo sfdisk ${DISK} <<-__EOF__
1M,48M,0x83,*
,,,-
__EOF__

sfdisk <= 2.25.x

sudo sfdisk --unit M ${DISK} <<-__EOF__
1,48,0x83,*
,,,-
__EOF__

Format Partition:With mkfs.ext4 1.43, we need to make sure metadata_csum and 64bit are disabled.
As the version of U-Boot needed for this target CAN NOT correctly handle reading files with these newer ext4 options.